Can two tanks be set up to run controlled experiments?

[fandaga]

I have 2 mixed reef tanks, roughly the same size (180g and 200g) and try to keep the parameters closely matched (Alk 9.0, Calc 450, Phos .08 Nitrate 5-10ppm) but they never match exactly. Lighting is the same. I often try something in 1 tank and see if it make a difference ie AB+ or reef roids etc. It's not scientifically super sound but it gives me an opportunity to see if certain things make a difference. It's also really nice to be able to swap corals from 1 tank to another if placement or flow isn't working and i don't have space in the same tank to move a coral.

Cool, so anything that you noticed which has made a noticeable difference? In my DT, I really can’t tell if daily dosing aminos, phyto, makes any impact.

 

[Faurek]

So if running an experiment where the measurable is growth, what corals would you choose and how many frags of each species?

Running the lighting test seems like it would be perhaps the easiest starting point to gain confidence in running such experiments.

That is the easiest part here.

 

[rhitee93]

I like to experiment as much as the next nerd. I think where this gets difficult is that each system is made up of millions of individual biological entities that don't care about your efforts to control variables. Each individual will do what it is genetically programmed to do at the best of its ability. Some will be better at their job than others.

My hypothesis is that any two systems, no matter how meticulously they are set up to be identical on day one, and given the same external stimuli, will still diverge in quantifiable ways.

 

[MnFish1]

I like to experiment as much as the next nerd. I think where this gets difficult is that each system is made up of millions of individual biological entities that don't care about your efforts to control variables. Each individual will do what it is genetically programmed to do at the best of its ability. Some will be better at their job than others.

My hypothesis is that any two systems, no matter how meticulously they are set up to be identical on day one, and given the same external stimuli, will still diverge in quantifiable ways.

Let's say one takes new equipment, everything the same - even Petri dishes. But - lets take my example of 2 5 gallon aquaria - It is actually very very simple to design a system that is basically identical for growing coral frags. Even adding live rock - though the pieces won't be identical, they will be identical enough to not make a difference on the coral growth.

However, I will agree with your point that they will diverge in 'quantifiable ways' - however, everything that is 'quantifiable' is not 'significant' to the results of the experiment. Medically, its the difference between 'statistical significance' and 'clinical significance'.

 

[fandaga]

That is the easiest part here.

Still, it’s an important question. How many frags of each would depend on how easy to get statistical significance. The more, the better. However, this would need to be balanced with cost and availability. Ten per tank seems like a safe number.

The species are also pretty important. I think would want species that are relatively robust, cheap, and easy to measure growth rates.

 

[fandaga]

I like to experiment as much as the next nerd. I think where this gets difficult is that each system is made up of millions of individual biological entities that don't care about your efforts to control variables. Each individual will do what it is genetically programmed to do at the best of its ability. Some will be better at their job than others.

My hypothesis is that any two systems, no matter how meticulously they are set up to be identical on day one, and given the same external stimuli, will still diverge in quantifiable ways.

So perhaps that’s the experiment then. Test two identical systems over 6 months to see if any statistically significant changes in coral growth between the two. I would assume there would be no statistically significant difference (p value of 0.05 or lower) in growth even with a very large sample size.

 

[rhitee93]

However, I will agree with your point that they will diverge in 'quantifiable ways' - however, everything that is 'quantifiable' is not 'significant' to the results of the experiment. Medically, its the difference between 'statistical significance' and 'clinical significance'.

True, "We" get to determine what is significant in this case. Perhaps that is the saving grace. The early part of my career was spent as a test engineer so I can get overly pedantic about what measurements actually mean.

So perhaps that’s the experiment then. Test two identical systems over 6 months to see if any statistically significant changes in coral growth between the two. I would assume there would be no statistically significant difference (p value of 0.05 or lower) in growth even with a very large sample size.

I don't know how meaningful it would be, but it would be fascinating to see just how closely you could keep two systems in sync without intervening. I'm pretty confident that the biology will add a lot of variability, but I've been wrong before. Just ask my wife :)

 

[fandaga]

True, "We" get to determine what is significant in this case. Perhaps that is the saving grace. The early part of my career was spent as a test engineer so I can get overly pedantic about what measurements actually mean.



I don't know how meaningful it would be, but it would be fascinating to see just how closely you could keep two systems in sync without intervening. I'm pretty confident that the biology will add a lot of variability, but I've been wrong before. Just ask my wife :)

I probably would just run with two control tanks then. I’ll have to see if I have enough budget for 3 systems.

 

[Faurek]

Well cheap glass boxes and AliExpress pumps should be enough, par38 LED's from AliExpress and you should be done for chemistry porpuse experiments. There is a 3w circulation pump that makes 3000l/h and I can tell you it's plenty powerful for manos, 1 of those could have SPS on a 5 gallon and 2 of those would be too much flow for some corals. I have it and it messed up heavy black substrate on a 10g freshwater.
Light experiments will be very expensive.

 

[fandaga]

Well cheap glass boxes and AliExpress pumps should be enough, par38 LED's from AliExpress and you should be done for chemistry porpuse experiments. There is a 3w circulation pump that makes 3000l/h and I can tell you it's plenty powerful for manos, 1 of those could have SPS on a 5 gallon and 2 of those would be too much flow for some corals. I have it and it messed up heavy black substrate on a 10g freshwater.
Light experiments will be very expensive.

Wow, par38 has to be the cheapest reef light. Very interesting.

 

[Dr. D]

Yes of course. Just never lose sight of the control parameters.

 

[Faurek]

Wow, par38 has to be the cheapest reef light. Very interesting.

Building my own is even cheaper, each LED color is around 1€ for 10, except violets and cyans for some reason those are expensive.
When you know what you are doing you can build lights way better than what companies sell for 400+ for less then 1/10 of that.

 

[fandaga]

Building my own is even cheaper, each LED color is around 1€ for 10, except violets and cyans for some reason those are expensive.
When you know what you are doing you can build lights way better than what companies sell for 400+ for less then 1/10 of that.

That’s awesome! I hope to see your tank build thread if you post in the future.

 

[Faurek]

That’s awesome! I hope to see your tank build thread if you post in the future.

I am starting what might be my end game nano at least for a few years right now and documenting it in a thread, it still has only 2 macroalgae and a few inverts, it will have softies, macroalgae and SPS including acros, mini sea squirts and sponges if I can find and doing it very cheap because I got unemployed quite a while ago, while also taking my degree.